The present invention relates to an arrangement for cooling oil in a gearbox in a vehicle by blowing cooling air over a coolant circuit which then cools the oil.
The oil in a vehicle gearbox has to be at a relatively low temperature if the components which are intended to be lubricated and cooled by the oil are to be able to achieve a long service life. A known way of ensuring that the oil in the gearbox will substantially continuously be at a sufficiently low temperature during operation of the vehicle is to use an air-cooled oil cooler for cooling the oil. However, an air-cooled oil cooler has to be so positioned in the vehicle that air which is at the temperature of the surroundings flows through it for it to be able to provide effective cooling of the oil. Air-cooled oil coolers are therefore often situated at the front portion of a vehicle at a location in front of, inter alia, the radiator for cooling the coolant of the combustion engine's cooling system. At this location the oil cooler has flowing through it a forced airflow which is at the temperature of the surroundings and is generated by a radiator fan during operation of the combustion engine. A disadvantage of such positioning of the oil cooler is that the oil has to be transported from the gearbox to the front portion of the vehicle. This entails having to lay relatively long oil lines in the vehicle. Moreover, for safety reasons, the presence of oil in such an exposed region as the front portion of a vehicle is to be avoided.
Another known practice is to use a liquid-cooled oil cooler for cooling of oil in a gearbox. The medium which such oil coolers use for cooling the oil is the existing coolant used in the cooling system for cooling the combustion engine. Liquid-cooled oil coolers may be situated in the vehicle close to the gearbox. In heavy vehicles, the coolant is usually cooled by a radiator situated downstream of a charge air cooler with respect to the intended direction of airflow through these cooling elements. The air is thus warmed by the charge air cooler before it can be used for cooling the coolant in the radiator. The coolant is thus cooled by air which is at a higher temperature than the surroundings. The coolant can therefore not usually be used for cooling the oil in the gearbox to a low enough temperature.